Risks and benefits of invasive epilepsy surgery workup with implanted subdural and depth electrodes

Abstract

SUMMARYPurpose: In patients with pharmacoresistant focal-onset seizures, invasive presurgical workup can identify epilepsy surgery options when noninvasive workup has failed. Yet, the potential benefit must be balanced with procedure-related risks. This study examines risks associated with the implantation of subdural strip and grid, and intracerebral depth electrodes. Benefit of invasive monitoring is measured by seizure outcomes. Diagnostic procedures made possible by electrode implantation are described. Methods: Retrospective evaluation of invasive workups in 242 epilepsy surgery candidates and additional 18 patients with primary brain tumors implanted for mapping only. Complications are scaled in five grades of severity. A regression analysis identifies risk factors for complications. Outcome is classified according to Engel's classification.Key Findings: Complications of any type were documented in 23% of patients, and complications requiring surgical revision in 9%. We did not find permanent morbidity or mortality. Major risk factor for complications was the implantation of grids and the implantation of electrode assemblies comprising strip and grid electrodes. Depth electrodes were significantly correlated with a lower risk. Tumors were not correlated with higher complication rates. Chronic invasive monitoring of 3-40 days allowed seizure detection in 99.2% of patients with epilepsy and additional extensive mapping procedures. Patients with epilepsy with follow-up >24 months (n = 165) had an Engel class 1a outcome in 49.7% if epilepsy surgery was performed, but only 6.3% when surgery was rejected. Significance: The benefit of chronic invasive workup outweighs its risks, but complexity of implantations should be kept to a minimum.

Evolution of cranial epilepsy surgery complication rates: a 32-year systematic review and meta-analysis

“…One explanation for rising complication rates could be the increasing use of larger or bilateral arrays and grids, which are associated with higher complication rates, compared with depth electrodes. 31,84 Another possible explanation could be an increasing sensitivity to complications and more careful documentation over time. However, it is also possible that surgeons are now performing fewer intracranial recordings, resulting in decreased surgical familiarity and increased complication potential.…”

Surgical management of medically refractory epilepsy due to early childhood stroke

“…Similar complication rates have been previously described in surgical series involving children who underwent staged epilepsy surgery. 24,38 Although staged resections necessitate more immediate discomfort, expense, and risk, the results in our series suggest that the likelihood of longerterm seizure control and low morbidity may justify this approach, particularly in light of the known association of porencephalic cysts and stroke-related foci to distant epileptogenic zones, and dual and sometimes triple pathologies giving rise to medically intractable seizures. 22 The temporary deficits incurred in our series, particularly in the setting of multilobar disconnections and hemispherotomies, are well-recognized side effects of major epilepsy operations.…”

Review of Epilepsy - Etiology, Diagnostic Evaluation and Treatment

“…Epilepsy surgery is an effective and safe alternative form of therapy for those patients with focal onset epilepsy [32,[42][43][44][45][46][47][48][49][50][51]. Major complications from epilepsy surgery and subdural electrode evaluation have an incidence of less than 7% and long term permanent deficits have an incidence of less than 2% [52][53][54][55][56][57][58]. An epilepsy surgery evaluation typically starts with long term video-EEG monitoring to confirm the diagnosis and type of focal onset epilepsy, establish the seizure type and seizure onset zone and determine the disabling effects of ictal behavior [42,59].…”